LAS VEGAS - OCTOBER 29: People vote early at the Meadows Mall October 29, 2008 in Las Vegas, Nevada. As of October 28, more than 32% of the Nevada electorate had cast their ballots ahead of the November 4 general election. (Photo by Ethan Miller/Getty Images)

Photo: Ethan Miller, Getty Images

LAS VEGAS - OCTOBER 29: People vote early at the Meadows Mall...

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Political consultant Jim Dobyns sits among voting machines and ballot boxes, which had been used in Palm Beach County during the 2000 presidential election of the infamous hanging chads, that he keeps in a storage unit in Pinellas Park , Fla., Thursday Oct. 16, 2008. (AP Photo/Steve Nesius)

U.S. Democratic Presidential nominee Barack Obama talks on his mobile phone as she prepares to step aboard his campaign plane in Norfolk, Virginia, October 29, 2008. Obama is campaigning in North Carolina and Florida on Wednesday before the November 4 presidential election. REUTERS/Jason Reed (UNITED STATES) US PRESIDENTIAL ELECTION CAMPAIGN 2008 (USA)

U.S. Republican presidential nominee Senator John McCain (R-AZ) points to the crowd as he takes the stage at a campaign rally at Everglades Lumber in Miami, Florida October 29, 2008. REUTERS/Brian Snyder (UNITED STATES) US PRESIDENTIAL ELECTION CAMPAIGN 2008 (USA)

The huge and potentially historic voter turnout expected next week is increasing chances for election day problems, including long lines, confusion at the polls and delays in counting ballots.

No one is predicting a repeat of the Florida meltdown of 2000, but election experts warn of shortages of voting machines in key states, a lack of trained poll workers, puzzling state rules on what ID voters must carry to the polls and purges of voter rolls in many states that could force thousands of voters to cast provisional ballots, which often go uncounted.

In battleground states such as Ohio and Indiana, election officials are bracing for a swarm of legal challenges by party officials over who is eligible to vote, stemming partly from GOP concerns over false voter registrations filed by the community organizing group ACORN.

The ugly side of politics is already on display in some states. In Virginia, a phony flyer that used the seal of the state election board informed voters in the Hampton Roads area that "due to the larger than expected voter turnout," the state Assembly had ruled that Republicans would vote on Tuesday and Democrats on Wednesday, a day after the election. State police are investigating the incident.

Election experts forecast a huge turnout, driven by intense interest in the presidential race and anxiety over an ailing economy and two wars. Curtis Gans, director of the Center for the Study of the American Electorate, is predicting that between 127 million and 132 million people will cast ballots - or 60.4 to 62.9 percent of those eligible to vote. That could exceed the recent high-water mark in voter participation set in 2004 - 60.7 percent - which was the highest since 1968, when 61.9 percent cast ballots.

Long waits

Even though a record number of people have voted early in many states, Gans said voters should brace for long waits on election day.

"We are going to have long lines," he said, adding that some states haven't added enough voting machines to keep pace. "But long lines in this election, as in 2004, are not going to deter people from voting, because of the emotional context of this election. They didn't deter people in 1992 or in 2004, and they're not going to deter people now."

Election experts are closely watching Virginia, a battleground state expecting a huge turnout and that requires only one voting machine for every 750 people. The Virginia NAACP sued the state's Gov. Tim Kaine, a Democrat, last week for failing to provide enough polling places and is asking a federal court to reallocate voting machines to precincts where high African American turnout is expected and to keep polls open for an extra two hours.

Voting equipment changes could spark further problems. Early voters in several counties in West Virginia and Tennessee recently complained that when they tried to vote for Democrats, the touch-screen voting machines registered their votes for Republicans.

Florida recently shifted back to optical scanners after touch-screen machines in Sarasota County didn't record any choice for 18,000 voters in a fiercely contested House race in 2006. But election officials now worry that the paper-fed optical scanners could add to delays and confusion for poll workers and voters.

California also has switched back to optical scanners because of concerns over the security and reliability of electronic voting. Nationwide, more than 40 percent of voters live in areas that have changed their voting equipment since 2004.

Voting rights advocates are most concerned about new rules that could allow legitimate voters to be removed from the rolls. Under the Help America Vote Act, which Congress passed in 2002, states have to maintain databases of all registered voters and double-check new voters' information against other state and federal databases. But advocates complain that even a typo by an election worker entering a voter's registration can lead to a name being purged.

Florida mismatches

Tova Wang, an election reform advocate for Common Cause, said more than 12,000 Florida voters are in limbo because of mismatches between their registration cards and the databases. Common Cause and election officials are trying to reach those voters before election day. Many of those voters will have to cast provisional ballots - which won't count unless they return within two days with documents establishing their identity.

Thirty county election officials in Florida, bucking a ruling by Republican Secretary of State Kurt Browning, plan to allow voters to fix their registration problems at the voting booth to avoid having to cast provisional ballots. Wang said, "You really want provisional ballots to be a last resort, not a first resort. They have such a big chance of not being counted."

In Ohio, Republicans have gone to court repeatedly to try to get the list of 200,000 new voters who don't match other databases - a prelude to challenging their eligibility at the polls. Ohio Secretary of State Jennifer Brunner, a Democrat, has resisted, saying typos and misspellings cause the vast majority of mismatches. The Supreme Court dismissed the case, but the White House last week asked the Justice Department to review whether those voters should have to reconfirm their registration before Tuesday to prevent voter fraud.

In Colorado, Common Cause and other groups are suing Secretary of State Mike Coffman, a Republican, alleging that he illegally removed more than 20,000 voter registrations because of mismatches. Coffman has disputed the charge, saying that just 2,454 registrations were removed because they were duplicates.

Tom Wilkey, executive director of the Election Assistance Commission, the agency created by Congress to improve the nation's election system, said voters can take steps to make sure their votes are counted: bring proper ID to the polls, read ballot instructions carefully and, if possible, vote early or during non-peak hours. Wilkey doesn't expect a replay of 2000, but he said some glitches are inevitable.

"The bottom line is, nationally, you are looking at 100,000 polling places and 13,000 election jurisdictions and anywhere from 1 to 2 million people that are involved and working that day as poll workers, technicians, drivers, you name it," Wilkey said. "That is an awfully big environment. Things can happen."

Tips to avoid problems at the polls

A huge turnout is expected Tuesday, but election officials say there are ways to avoid problems.

Double-check your registration: Call the elections office if you're concerned you're not registered. The deadline to register in California was Oct. 20.

Know your polling place: If you don't know, call the elections office or ask a neighbor.

Vote during off-peak hours: The busiest times for voting are the morning commute, the lunch hour, 3 to 6 p.m. and just before polls close. Polls will be open from 7 a.m. to 8 p.m.

Vote early: Any California voter can vote by mail, but the deadline to request a mail-in ballot was Tuesday. Some California counties, including San Francisco, allow early voting in person. Check with your county elections office.

Read ballot instructions: The most common reason ballots are rejected is a failure to follow instructions for marking ballots.